One patient of sepsis by P. aeruginosa after the implanting of a ventriculoatrial valve following extirpation of an expansive intracranial process is studied. During the evolution of the septic process there appeared an associated nephrotic syndrome with histologic lesions corresponding to an acute exudative glomerular nephritis. The germ became resistant to the antibiotics used, carbenicillin plus gen-tamicin, being later sensitive only to fosfomycin with which finally complete cure was achieved.